CHARACTERIZATION, CLASSIFICATION AND EVALUATION OF SOILS IN CHILLAKUR MANDAL OF SPSR NELLORE DISTRICT, ANDHRA PRADESH
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Date
2015
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Acharya N.G. Ranga Agricultural University, Guntur
Abstract
The present investigation involves characterization, classification and evaluation of soils in Chillakur mandal of SPSR Nellore district, Andhra Pradesh. For this, seven representative pedons were selected in seven different locations of the study area covering all types of soils. All the seven pedons were described for their morphological features in the field and horizon-wise samples were collected and analyzed in the laboratory for physical, physico-chemical and chemical properties.
The study area was characterized by semi-arid monsoonic climate with distinct summer, winter and rainy seasons. The pedons selected were located on nearly plain (0-1%) to gently sloping (1-3%) topography. All pedons were developed from granite-gneiss parent material except pedon 7, which was originated from alluvium. The morphological features indicated the presence of AC (Pedons 1, 3, 4 and 7) and ABC (Pedons 2, 5 and 6) profiles. The soils were moderately deep to very deep in depth, pale brown to dark reddish brown in colour, sandy to clay loam in texture and had crumb to angular blocky structure.
The clay content decreased with depth in pedons 1and 4 while pedons 5 and 6 showed an increasing trend up to Bw2 and Bw3 horizons,
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respectively later on a decreasing trend with depth. Pedon 3 showed an increasing trend with depth. However, no specific trend with depth was observed in pedons 2 and 7. Physical constants like water holding capacity, loss on ignition and volume expansion followed the trend of clay content. All pedons exhibited an irregular trend of bulk density with depth while pedon 1 showed a decreasing trend, corresponding to decreasing organic carbon content with depth.
The pedons were slightly acidic to moderately alkaline in reaction, non-saline and low to medium in organic carbon. All the pedons registered low CaCO3 status. CEC values were low to medium and exchange complex was dominated by Ca+2 followed by Mg+2, Na+ and K+. Chemical composition of soils revealed that all the pedons had high silica content indicating siliceous nature.
Regarding nutrients status, the soils were low to medium in available nitrogen and available phosphorus, low to high in available potassium and high in available sulphur. However, soils were deficient in available zinc and sufficient in available copper, iron (except pedon 7) and manganese.
Based on morphological, physical, physico-chemical, mineralogical and meteorological data, the soils of Chillakur mandal were classified as:
Pedon 1 : Fine-loamy, mixed, isohyperthermic, Typic Ustorthent
Pedon 2 : Fine-loamy, smectitic, isohyperthermic, Typic Haplustept
Pedon 3 : Fine-loamy, smectitic, isohyperthermic, Typic Ustorthent
Pedon 4 : Fine-loamy, kaolinitic, isohyperthermic, Typic Ustorthent
Pedon 5 : Fine-loamy, smectitic, isohyperthermic, Typic Haplustept
Pedon 6 : Fine-loamy, mixed, isohyperthermic, Typic Haplustept
Pedon 7 : Sandy, siliceous, isohyperthermic, Typic Ustipsamment
Based on the soil properties, the soils of the Chillakur mandal have been classified into land capability classes and sub-classes viz., IIIs (Pedons 5 and 6), IIIws (Pedon 2), IVs (Pedon 7), IVse (Pedons 1, 3 and 4).
The soil-site suitability evaluation of study area revealed that all pedons were marginally suitable (S3) for rice, groundnut, sesame and sunflower crops except pedon 7 which is temporarily not suitable (N1) for rice crop.
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D5154
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